Correlative rotational cells, which have heretofore been used for carrying out a method of correlative analysis or fluorescence analysis, are usually driven by a synchronous motor or the like, either directly or indirectly, as shown in FIGS. 1a and 1b, in order to rotate the cell at a high speed. In the structure shown in FIG. 1(a), a correlative rotational cell C.sub.1 is directly mounted on the shaft S.sub.1 of a motor M.sub.1 having a rotor R within it. This is an example of an arrangement in which the cell is directly rotated by the motor and the structure is clearly rather simple. However, it is a disadvantage of this type of structure that sometimes optical noises occur due to the oscillation of the shaft. Further, in the arrangement of FIG. 1(b), the rotational shaft S.sub.2 of a motor M.sub.2 and the shaft S.sub.3 of a rotational cell C.sub.2 are positioned parallel to each other and pulleys P.sub.1 and P.sub.2 which are mounted on the corresponding shafts S.sub.2 and S.sub.3 are connected by a driving belt B. This arrangement is an example in which the cell is directly rotated by the motor. The disadvantages of this type of structure are that it is rather complicated and moreover, sometimes, noises appear due to the inconsistency of the rotational motion, originating from the system of power transmission.